Other police agencies said seating someone on the bumper of a patrol car is not an unusual practice.

Brown said sheriff's deputies lean suspects against a car, over a car hood or make them sit on a bumper. There's no requirement to place them inside, he said.

"It's not at all uncommon what that officer did," he said. "We do it all the time."

But it's clear that officers are responsible for what happens to those being detained or arrested.

Chris Krankemann, a Santa Rosa personal injury lawyer, said police can be liable if they leave someone in a vulnerable position and they get hurt.

If someone is drunk, Krankemann said police could have a heightened obligation to protect them. They could be found negligent if they don't, he said.

"Negligence is a failure to use reasonable care," Krankemann said. "Certainly, in putting a drunk person on a bumper it's foreseeable that they could get up and walk around. The key is what did the officer know?"

But the blame could shift to the suspect if they contributed to the accident. Walking into traffic to get away or to try to commit suicide would relieve the officer of some liability, Emery said.

"There is a duty, but it's a duty defined by what's reasonable under the circumstances," Emery said.

Investigators said Higgins and his 53-year-old girlfriend were passengers in her adult son's car sometime before 9:30 p.m.

The couple began to fight and Higgins punched the son, who pulled over in Windsor near the southbound Shiloh Road off ramp, Sonoma County Sheriff's Lt. Steve Brown said.

A passing CHP officer saw the car and stopped to check it out.

The officer saw Higgins drag the woman out and throw her to the ground, Brown said.

He handcuffed Higgins and sat him on the front bumper of his patrol car, Brown said.

When the girlfriend and son started yelling and walking toward the officer, Higgins stood up and walked in front of an oncoming car, Brown said.

He suffered broken bones and was taken to Santa Rosa Memorial Hospital where he had been listed in critical condition.

Higgins had a blood-alcohol content of 0.36 percent, more than four times the legal limit of 0.08, Brown said.

He's expected to be charged with domestic battery and making terrorist threats and could be arraigned while he recovers in the hospital, Brown said.

Meanwhile, the CHP is conducting its own investigation. The officer's name wasn't released.

Capt. Greg Tracey said the state agency does not have a specific policy outlining steps officers must take in safeguarding handcuffed people.

Instead, the officers are asked to use their best judgment considering the circumstances, he said.

"No two enforcement contacts are the same," he said. "Many are so dynamic, that while an officer is making decisions about what to do, the incident circumstances change."

Spokesman Jon Sloat said the officer in the Higgins case remains on regular duty.

Other police agencies said seating someone on the bumper of a patrol car is not an unusual practice.

Brown said sheriff's deputies lean suspects against a car, over a car hood or make them sit on a bumper. There's no requirement to place them inside, he said.

"It's not at all uncommon what that officer did," he said. "We do it all the time."

But it's clear that officers are responsible for what happens to those being detained or arrested.

Chris Krankemann, a Santa Rosa personal injury lawyer, said police can be liable if they leave someone in a vulnerable position and they get hurt.

If someone is drunk, Krankemann said police could have a heightened obligation to protect them. They could be found negligent if they don't, he said.

"Negligence is a failure to use reasonable care," Krankemann said. "Certainly, in putting a drunk person on a bumper it's foreseeable that they could get up and walk around. The key is what did the officer know?"

But the blame could shift to the suspect if they contributed to the accident. Walking into traffic to get away or to try to commit suicide would relieve the officer of some liability, Emery said.

"There is a duty, but it's a duty defined by what's reasonable under the circumstances," Emery said.